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  <div id="hd"><h1><a href="./">JSCoverage</a><br><span class="tag">code coverage for JavaScript</span></h1></div>  
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        <h2><abbr title="Frequently Asked Questions">FAQ</abbr></h2>

        <h3>Can I use JSCoverage to measure code coverage for a page on <code>http://example.com/</code>?</h3>

        <p>
        In order to measure the code coverage of a page on <code>http://example.com/</code>,
        you must run <code>jscoverage</code> to create a <code>jscoverage.html</code> file on the
        <code>example.com</code> server.  You cannot use <code>http://example.org/jscoverage.html</code>
        to measure the code coverage of a page located on <code>http://example.com/</code>.
        </p>

        <p>
        The fundamental reason for this limitation is the
        <a href="http://www.mozilla.org/projects/security/components/same-origin.html">Same Origin Policy</a>
        for untrusted JavaScript.
        </p>

        <p>
        (In fact, the current version of JSCoverage is slightly more restrictive
        than this: it requires that the JavaScript being measured reside under the
        same <strong>directory</strong> as the <code>jscoverage.html</code> file.)
        </p>

        <h3 id="jscoverage-vs-jscoverage-server">Should I use the <code>jscoverage</code> program or the <code>jscoverage-server</code> program?</h3>
        <p>
        First, note that the <code>jscoverage</code> program and the <code>jscoverage-server</code> program are mutually exclusive alternatives;
        you must use one or the other, but not both.  If you try to use both at the same time you will get strange results.
        </p>
        <p>
        Which of the two programs you use is largely a matter of personal preference.
        The <code>jscoverage-server</code> program has some additional features,
        such as the ability to store coverage reports to disk.
        However, the <code>jscoverage</code> program is the more mature of the two and is generally easier to use;
        this program is recommended if you do not need any of the additional features of <code>jscoverage-server</code>.
        </p>

        <h3>Why doesn't my test suite run under JSCoverage in Firefox 3?</h3>

        <p>
        Firefox 3 introduces <a
        href="http://tech.groups.yahoo.com/group/jsunit/message/1075">new
        security restrictions</a> on local files.  Depending on the way your
        test suite is organized, this may cause problems for JSCoverage.
        (You may get the error "uncaught exception: Permission denied to get property Window._$jscoverage".)
        There are several workarounds:
        </p>

        <ul class="list">
        <li><p>Place your files on a web server instead of loading them from the file system.
            This is usually the simplest solution.</p>
        <li><p>Organize your HTML files in your test suite in a flat directory structure.  For example, suppose that
            you instrument your test suite with this command:</p>
<pre>
jscoverage src instrumented
</pre>
            <p>If all your HTML files are located directly under the <code>src/</code> directory (i.e., not in a
            subdirectory of <code>src/</code>), then you should not have any problems using Firefox 3.</p>
        <li><p>Set the <a href="http://kb.mozillazine.org/Editing_configuration">Firefox preference</a> named 
            <code><a href="http://kb.mozillazine.org/Security.fileuri.origin_policy">security.fileuri.origin_policy</a></code>
            to 3.</p>
        </ul>

        <h3>I'm trying to load my code with the URL
        <code>file:///C:/foo/bar/jscoverage.html?foo/bar.html</code>
        and I'm getting all kinds of JavaScript errors.</h3>

        <p>
        Internet Explorer 6 seems to have problems with a <code>file:</code> URL
        that has a query string with a slash in it.
        </p>
        <p>
        As a workaround:
        </p>
        <ul class="list">
        <li><p>Place your files on a web server instead of loading them from the file system.
            (<code>http:</code> URLs work fine.)</p>
        <li><p>Do not use a query string; enter your URL in the "URL" field in the "Browser" tab.</p>
        <li><p>Rearrange your directory structure so that <code>bar.html</code>
            ends up in the same directory as <code>jscoverage.html</code>; then
            you can use the URL
            <code>file:///C:/foo/bar/jscoverage.html?bar.html</code>
            with no slash in the query string.</p>
        <li><p>Use a different browser.  (IE 7 seems to work.)</p>
        </ul>

        <h3>JSCoverage changes my cursor to a busy cursor, and it never changes back!</h3>

        <p>
        Certain browsers (<i>e. g</i>., Internet Explorer 6, Opera, Safari) have trouble changing
        the cursor.  Try moving the mouse and your cursor should change back to normal.
        </p>

        <p>
        See <a href="http://groups.google.com/group/Google-Web-Toolkit/browse_thread/thread/631908bd63241136/783c307480f95d8c">this discussion</a> for more information.
        </p>

        <h3>JSCoverage hangs sometimes when rendering the coverage report.</h3>

        <p>
        With Internet Explorer 6 (I think I see a pattern here), garbage collection can cause performance problems.
        (More information <a href="http://ajaxian.com/archives/garbage-collection-in-ie6">here</a>.)
        </p>

        <h3 id="jsunit">Can JSCoverage be used with <a href="http://www.jsunit.net/">JsUnit</a>?</h3>

        <p>
        It is necessary to run JSCoverage in <dfn>inverted mode</dfn>.  You will have to
        modify JsUnit to launch JSCoverage.
        </p>

        <p>
        See the directory <code>doc/example-jsunit</code> for an example. It
        contains a copy of JsUnit version 2.2alpha11, with the file
        <code>jsunit/app/main-data.html</code> slightly modified to add a button
        which launches JSCoverage.  It also contains a simple unit test file <code>test.html</code>.  You
        can instrument this example as follows:
        </p>

<pre>
jscoverage --no-instrument=jsunit doc/example-jsunit doc/instrumented-jsunit
</pre>

       <p>
       You can then run the <code>test.html</code> file in JsUnit's <code>jsunit/testRunner.html</code>.
       The simplest way to do this is probably to copy the contents of <code>doc/instrumented-jsunit</code>
       to the root of a web server and then access the URL
       </p>

<pre>
http://127.0.0.1/jsunit/testRunner.html?testPage=http://127.0.0.1/test.html&amp;autoRun=true
</pre>

      <p>
      After the test suite has been run, click on the "Coverage report" button
      to get a coverage report.
      </p>

      <h3 id="ie-proxy">Does Internet Explorer work with <code>jscoverage-server --proxy</code>?</h3>

      <p>
      Internet Explorer <a href="http://www.fiddler2.com/fiddler/help/hookup.asp#Q-LocalTraffic">does
      not use a proxy for URLs with host <code>127.0.0.1</code> or
      <code>localhost</code></a>.
      The proxy <em>will</em> be used if you use your machine's actual IP
      address or host name.
      For example, if your IP address is <code>192.168.100.100</code>, you can
      access a URL like <code>http://192.168.100.100/jscoverage.html</code> in
      Internet Explorer and it will work.
      (Under Windows, you can get your machine's IP address with the <code>ipconfig</code> command.)
      </p>
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